Door latch and interlock



s p 950 o. H. BEYMER EI'AL 2,521,498

DOOR LATCH AND INTERLOCK Filed Dec. 2, 1947 Fig. 5.

Inventors Oliver, H. Beymer,

William H. Ne'sbit,

Their Atorrjey.

door.

Patented Sept. 5, 1950 UNITED STATES PATENT OFFICE I noon LATCH AND INTERLOCK Oliver H. Beymer and William H. Nesbit, Pittsfield, Mass, assignors to General Electric Company, a corporation of New York 1 Application December 2, 1947, Serial No. 789,300

This invention relates to door latches and more particularly to door latches of the interlocking type whose operation prescribes the sequence of opening and shutting a series of adjacent doors. It is often required where two adjacent doors are separated by a'door jamb, that one of the doors have a concealed lock and that this lock should be' available only by opening the other Also, the lock and latch must be made fool-proof so that it cannot be jimmied out of the locked position when both doors are closed.

It is diflicult to provide an ordinary type of latch which will satisfy the prescribed conditions. First of all the material from which the door and door jamb is constructed is usually thin making it impossible to recess handles, knobs or stops. Also,

' the clearance between the door and door jamb is usually made as small as practical thus allowing little or no space for a handle, stop or latch. In

' the case where the two doors are separated by a so that the operation of any door is dependent upon the'ad'joining ones. y V

Another object of the invention is to provide in such a system a means for mechanically looking a 'pluralityof doors using concealed locks for all but one, or the master door.

Still another object of the invention is to provide a simple and improved means for mechanically interlocking a plura'lity'of doors in such a way as to prescribe a certain sequence of operation in opening the doors and the reverse sequence in closing the doors.

The invention will be better understood fromthe following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Fig. 1 shows a plan view of a unit sub-station composed of three compartments having a door in the front of each one. Figs. 2, 3, and 4 show a plan view, side elevation through the section 3-3 of Fig.2, and back elevation respectively of a preferred form of the latch mechanism. Fig. 5 i s a plan view of the doors ajar. Fig. 6 is a plan view of an alternative latch construction.

Fig. 7 is a plan view of a mechanism for interlocking the doors. Fig. 8 is a front elevation of the same device. Fig. 9 is a side elevation of the interlocking mechanism through the section 2 Claims. (Cl. 292146) 99 of Fig. 8. Fig. 10 is a side elevation through the section lO-Iil of Fig. 8. Fig. 11 is a plan view of an alternative mechanism for interlocking the doors. Fig. 12 is a side elevation of thisiinterlocking device through the section I2-l2 of Fig. 11.

Referring now to the drawing there is shown in Fig. '1; by .way of example, a unit sub-station l composed of three compartments 2, 3, and 4 each having respectively a door 5, 6, and 1. Door '5 is the master door--sub-door 6 can only be opened after door 5 has been opened; adjacent door T cannot be opened before sub-door 6. Thus, the opening operation must start at the master door 5 and continue, in the illustrated case, sequentially to the left. Similarly, it will be shown that the closing operation must follow the reverse order. Fig. 2 shows a preferred form of the interlocking mechanism between the master door 5'and sub-door 6 in an enlarged view. Master door 5 is supported by hinge 8, and both doors, 5 and 6 close against the same door jamb 9. Master door 5 may be locked by some external locking mechanism (not illustrated) whereas the sub-doors are held closed by a concealed latch III which has a cylindrical body or bolt I l with a' taperat one end l2 and at the other end, two handles or arms I3 and M which may be an integral part of the body II. The latch ID passes throughfthe'door jamb 9 intoa hole in the sub-door 6. Master door 5 is slotted so that the latch l6 passes through it, but does not prevent door 5 from opening. The handles l3 and I4 are approximately perpendicular to each other so that when latch I0 is in the closed position handle [3 lies in the horizontal and extends toward the rear of door 5 where it rests in a notch l f a notched locking plate 1 6. The side of the notch l5 is sloped slightly so as to wedge the bolt l9 farther into the locked position in door 6. When the doors 5 and 8 are closed handle 14 extends approximately vertically upward, and master door 5 closes flush against the bolt I0, thus preventingrotation of the latch bolt Hi and consequently it cannot be jimmied out of the locked position since vertical handle it will not allow the horizontal handle is to be moved from the notch l5.

In order to operate the latch Ill it is first necessary to open the master door 5; rotate the handle, as shown inFig. 3, so that the horizontal handle 13 is raised out of the notch' l5 and clears the notched locking plate It. The latch bolt it may then be moved to the right until the stop I! strikes the door jamb 9 as shown in Fig. 5. The stop I! also prevents the removal of latch bolt 10 from the door jamb 9. Sub-door 6 may now be opened as shown in Fig. 5.

When the bolt I is in the open position master door 5 cannot be closed because of interference with handle [4.

A variation of this arrangement for locking is shown in Fig. 6. This is similar to the method already disclosed except that a wedge block 18 may be made an integral part of door 5 so that when door 6 is closed and latch I9 is in the closed position the wedge l8 presses against the latch bolt l9 holding it securely locked andpreventing it from being jimmied out of the locked. position. When the latch bolt 19 is in the open position door 5 cannot be closed because the wedge block I8 strikes against the latch bolt 19 as shown in Fig. 6. Thisalternative construction has the advantage of using a simpler latch, but the preferred form of the invention has the advantage of having the latch and locking mechanism independent of the zdoor.

It :can be :seen that the latch bolts It! and it can be returned to the closed :position without closing sub-door 15. Therefore, .master :door 5 "can be closed whilesub-door 6 is still open. In order to remedy this situation some form of interlock mechanism which makes it extremely difficult to close the master door 5 without first closing subdoor 6 is necessary. Two forms of such interlocking mechanisms are shown in Figs. 7-12.

Door jam'b 8 in Fig. 7 is provided with a bar 320 and .a block2l to which is attached a rod and plate assembly 22 by means of a pin v23 and a shim 24. The rods on assembly 22 extend through slots 25 and :25, Figs. :9 and 10, indoor jamb 3. When doors Eand -B are both closed assembly .22 is in a horizontal {position and the rods engage :notches 27 and 28 indoors 5 "and 5. When master -door 5 is opened (this must be-done to :release the latch bolt for door-fi-as previously explained) assembly 2-2 remains in a horizontal position. But when the latchbolt for door 6 is released and door 15 is opened, the assembly 22 drops by gravity, since pin 2-3 is offset -from*the center line of door jamb :9, .from the horizontal position shown in Fig. 9 to the inclined position. If door 6 is "closed first assembly 2-2 rides up on the slope of notch 21 and returns to a horizontal position; thus, lining up the other end of assembly 22 with notch 28 allowing door '5 to "close. But if it is attempted to =close door 5 first the edge of door -5 will strike against assembly 22 which is in the inclined position shown in Fig-8 making it impossible to close door 5. Any :series-of-doors may be interlocked in this fashion.

Another arrangement for interlocking the doors is shown in Figs. '11 and 12. Door 6, in Fig. 11 is provided with a pin .29 which, when door 5 is closed, passes through the opening 30 in the'door jamb 9. The pin 29 forces'a striker plate-3i which is an integral part of an interlock 32, as shown in Fig. 12, toward the back of a guard 33.

Also "as shown in Fig. 12 this moves the interlock 32 which is pivoted about pin 34 so that notch -35, which has a diameter slightly larger than that of the latch ill, will correspond with the hole .35 through the door jamb .9. Thus, allowving latch bolt 1.0 tobe moved to theleftand looking sub-door -6.

When door 6 is opened .pin 2.9 is withdrawn from opening 30 and due to the location of the center of gravity of interlock 32 it falls into the position shown by the solid outline of the interlock 32 in Fig. 12. The hole 36 in the door jamb 9 is partially covered by the interlock 32 so that it is impossible for the latch bolt ID to be placed in the closed position. It can only be moved to the left when hole 36 and :notch 35 are in correspondence and this isonly achieved when subdoor 6 is closed.

The arrangements previously described for locking and interlocking two adjacent doors are not limited to the case used in the preceding discussion where both doors close against the same door jamb. Consider doors 6 and l as shown in Fig. 1. Door 1 closes against door jamb 31, but door 6 is attached to door jamb 31 by hinge 38. The latch bolt l9 passes through both the door jamb 31 and the hinge 38, and the doors 6 and 1 are interlocked in the same way as doors 5 and 6. Thus any series of doors can :be locked and *interlocked in this manner.

While there have been shown and described particular embodiments of the'invention, it'will be obvious to those skilled inthe art that changes and modifications can 'be made .without departing from the invention, and, therefore, it fis aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention, as claimed.

What we claim as new and desire to secure by Letters Patent-of the United States is:

1. An interlocking door latch :system for mounting in a door 'jamb which .is between :a hinged master door cooperating with one side of said jamb and a hinged sub-door which closes against the other side of said jamb, comprising a bolt slidable along and rotatable about its axis in said jamb, said sub-door having a hole for receiving an end of said bolt when said --subdoor is closed and said bolt is slid toward said sub door for latching said sub door -'closed, a pairof arms attached to the other end of said :bolt and extending at right angles to the axis of saidbolt and at right angles to-each other, andanotched plate associated with said Idoor jamb, the notches in said plate being so located and proportioned as to receive one of said arms :ina position perpendicular to said master door only when said bolt has been moved along its axis into its latched position of said sub-door, said arms and plate.cooperating to prevent closure of said master door when said bolt is in any other axialiposition, said notch preventing movement of said bolt from its latching position of :said sub-door except when said master door is open.

2. An interlocking door latch system :asdefined in claim 21 combined with additional interlock means for preventing closure of :said main :dcor until after said sub-door has 'been closed.

GLI-VER BEYNER.

WILLIAM H. .NESBIT.

REFERENCES CITED The following references .are of record :in th file of this patent:

UNITED STATES PATENTS Name .Date

2,320,849 Claybournet a1. June V1, 1943 

